Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 377 insertions, 0 deletions

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+Dynamic debug
++++++++++++++
+
+
+Introduction
+============
+
+Dynamic debug allows you to dynamically enable/disable kernel
+debug-print code to obtain additional kernel information.
+
+If ``/proc/dynamic_debug/control`` exists, your kernel has dynamic
+debug.  You'll need root access (sudo su) to use this.
+
+Dynamic debug provides:
+
+ * a Catalog of all *prdbgs* in your kernel.
+   ``cat /proc/dynamic_debug/control`` to see them.
+
+ * a Simple query/command language to alter *prdbgs* by selecting on
+   any combination of 0 or 1 of:
+
+   - source filename
+   - function name
+   - line number (including ranges of line numbers)
+   - module name
+   - format string
+   - class name (as known/declared by each module)
+
+Viewing Dynamic Debug Behaviour
+===============================
+
+You can view the currently configured behaviour in the *prdbg* catalog::
+
+  :#> head -n7 /proc/dynamic_debug/control
+  # filename:lineno [module]function flags format
+  init/main.c:1179 [main]initcall_blacklist =_ "blacklisting initcall %s\012
+  init/main.c:1218 [main]initcall_blacklisted =_ "initcall %s blacklisted\012"
+  init/main.c:1424 [main]run_init_process =_ "  with arguments:\012"
+  init/main.c:1426 [main]run_init_process =_ "    %s\012"
+  init/main.c:1427 [main]run_init_process =_ "  with environment:\012"
+  init/main.c:1429 [main]run_init_process =_ "    %s\012"
+
+The 3rd space-delimited column shows the current flags, preceded by
+a ``=`` for easy use with grep/cut. ``=p`` shows enabled callsites.
+
+Controlling dynamic debug Behaviour
+===================================
+
+The behaviour of *prdbg* sites are controlled by writing
+query/commands to the control file.  Example::
+
+  # grease the interface
+  :#> alias ddcmd='echo $* > /proc/dynamic_debug/control'
+
+  :#> ddcmd '-p; module main func run* +p'
+  :#> grep =p /proc/dynamic_debug/control
+  init/main.c:1424 [main]run_init_process =p "  with arguments:\012"
+  init/main.c:1426 [main]run_init_process =p "    %s\012"
+  init/main.c:1427 [main]run_init_process =p "  with environment:\012"
+  init/main.c:1429 [main]run_init_process =p "    %s\012"
+
+Error messages go to console/syslog::
+
+  :#> ddcmd mode foo +p
+  dyndbg: unknown keyword "mode"
+  dyndbg: query parse failed
+  bash: echo: write error: Invalid argument
+
+If debugfs is also enabled and mounted, ``dynamic_debug/control`` is
+also under the mount-dir, typically ``/sys/kernel/debug/``.
+
+Command Language Reference
+==========================
+
+At the basic lexical level, a command is a sequence of words separated
+by spaces or tabs.  So these are all equivalent::
+
+  :#> ddcmd file svcsock.c line 1603 +p
+  :#> ddcmd "file svcsock.c line 1603 +p"
+  :#> ddcmd '  file   svcsock.c     line  1603 +p  '
+
+Command submissions are bounded by a write() system call.
+Multiple commands can be written together, separated by ``;`` or ``\n``::
+
+  :#> ddcmd "func pnpacpi_get_resources +p; func pnp_assign_mem +p"
+  :#> ddcmd <<"EOC"
+  func pnpacpi_get_resources +p
+  func pnp_assign_mem +p
+  EOC
+  :#> cat query-batch-file > /proc/dynamic_debug/control
+
+You can also use wildcards in each query term. The match rule supports
+``*`` (matches zero or more characters) and ``?`` (matches exactly one
+character). For example, you can match all usb drivers::
+
+  :#> ddcmd file "drivers/usb/*" +p	# "" to suppress shell expansion
+
+Syntactically, a command is pairs of keyword values, followed by a
+flags change or setting::
+
+  command ::= match-spec* flags-spec
+
+The match-spec's select *prdbgs* from the catalog, upon which to apply
+the flags-spec, all constraints are ANDed together.  An absent keyword
+is the same as keyword "*".
+
+
+A match specification is a keyword, which selects the attribute of
+the callsite to be compared, and a value to compare against.  Possible
+keywords are:::
+
+  match-spec ::= 'func' string |
+		 'file' string |
+		 'module' string |
+		 'format' string |
+		 'class' string |
+		 'line' line-range
+
+  line-range ::= lineno |
+		 '-'lineno |
+		 lineno'-' |
+		 lineno'-'lineno
+
+  lineno ::= unsigned-int
+
+.. note::
+
+  ``line-range`` cannot contain space, e.g.
+  "1-30" is valid range but "1 - 30" is not.
+
+
+The meanings of each keyword are:
+
+func
+    The given string is compared against the function name
+    of each callsite.  Example::
+
+	func svc_tcp_accept
+	func *recv*		# in rfcomm, bluetooth, ping, tcp
+
+file
+    The given string is compared against either the src-root relative
+    pathname, or the basename of the source file of each callsite.
+    Examples::
+
+	file svcsock.c
+	file kernel/freezer.c	# ie column 1 of control file
+	file drivers/usb/*	# all callsites under it
+	file inode.c:start_*	# parse :tail as a func (above)
+	file inode.c:1-100	# parse :tail as a line-range (above)
+
+module
+    The given string is compared against the module name
+    of each callsite.  The module name is the string as
+    seen in ``lsmod``, i.e. without the directory or the ``.ko``
+    suffix and with ``-`` changed to ``_``.  Examples::
+
+	module sunrpc
+	module nfsd
+	module drm*	# both drm, drm_kms_helper
+
+format
+    The given string is searched for in the dynamic debug format
+    string.  Note that the string does not need to match the
+    entire format, only some part.  Whitespace and other
+    special characters can be escaped using C octal character
+    escape ``\ooo`` notation, e.g. the space character is ``\040``.
+    Alternatively, the string can be enclosed in double quote
+    characters (``"``) or single quote characters (``'``).
+    Examples::
+
+	format svcrdma:         // many of the NFS/RDMA server pr_debugs
+	format readahead        // some pr_debugs in the readahead cache
+	format nfsd:\040SETATTR // one way to match a format with whitespace
+	format "nfsd: SETATTR"  // a neater way to match a format with whitespace
+	format 'nfsd: SETATTR'  // yet another way to match a format with whitespace
+
+class
+    The given class_name is validated against each module, which may
+    have declared a list of known class_names.  If the class_name is
+    found for a module, callsite & class matching and adjustment
+    proceeds.  Examples::
+
+	class DRM_UT_KMS	# a DRM.debug category
+	class JUNK		# silent non-match
+	// class TLD_*		# NOTICE: no wildcard in class names
+
+line
+    The given line number or range of line numbers is compared
+    against the line number of each ``pr_debug()`` callsite.  A single
+    line number matches the callsite line number exactly.  A
+    range of line numbers matches any callsite between the first
+    and last line number inclusive.  An empty first number means
+    the first line in the file, an empty last line number means the
+    last line number in the file.  Examples::
+
+	line 1603           // exactly line 1603
+	line 1600-1605      // the six lines from line 1600 to line 1605
+	line -1605          // the 1605 lines from line 1 to line 1605
+	line 1600-          // all lines from line 1600 to the end of the file
+
+The flags specification comprises a change operation followed
+by one or more flag characters.  The change operation is one
+of the characters::
+
+  -    remove the given flags
+  +    add the given flags
+  =    set the flags to the given flags
+
+The flags are::
+
+  p    enables the pr_debug() callsite.
+  _    enables no flags.
+
+  Decorator flags add to the message-prefix, in order:
+  t    Include thread ID, or <intr>
+  m    Include module name
+  f    Include the function name
+  s    Include the source file name
+  l    Include line number
+
+For ``print_hex_dump_debug()`` and ``print_hex_dump_bytes()``, only
+the ``p`` flag has meaning, other flags are ignored.
+
+Note the regexp ``^[-+=][fslmpt_]+$`` matches a flags specification.
+To clear all flags at once, use ``=_`` or ``-fslmpt``.
+
+
+Debug messages during Boot Process
+==================================
+
+To activate debug messages for core code and built-in modules during
+the boot process, even before userspace and debugfs exists, use
+``dyndbg="QUERY"`` or ``module.dyndbg="QUERY"``.  QUERY follows
+the syntax described above, but must not exceed 1023 characters.  Your
+bootloader may impose lower limits.
+
+These ``dyndbg`` params are processed just after the ddebug tables are
+processed, as part of the early_initcall.  Thus you can enable debug
+messages in all code run after this early_initcall via this boot
+parameter.
+
+On an x86 system for example ACPI enablement is a subsys_initcall and::
+
+   dyndbg="file ec.c +p"
+
+will show early Embedded Controller transactions during ACPI setup if
+your machine (typically a laptop) has an Embedded Controller.
+PCI (or other devices) initialization also is a hot candidate for using
+this boot parameter for debugging purposes.
+
+If ``foo`` module is not built-in, ``foo.dyndbg`` will still be processed at
+boot time, without effect, but will be reprocessed when module is
+loaded later. Bare ``dyndbg=`` is only processed at boot.
+
+
+Debug Messages at Module Initialization Time
+============================================
+
+When ``modprobe foo`` is called, modprobe scans ``/proc/cmdline`` for
+``foo.params``, strips ``foo.``, and passes them to the kernel along with
+params given in modprobe args or ``/etc/modprob.d/*.conf`` files,
+in the following order:
+
+1. parameters given via ``/etc/modprobe.d/*.conf``::
+
+	options foo dyndbg=+pt
+	options foo dyndbg # defaults to +p
+
+2. ``foo.dyndbg`` as given in boot args, ``foo.`` is stripped and passed::
+
+	foo.dyndbg=" func bar +p; func buz +mp"
+
+3. args to modprobe::
+
+	modprobe foo dyndbg==pmf # override previous settings
+
+These ``dyndbg`` queries are applied in order, with last having final say.
+This allows boot args to override or modify those from ``/etc/modprobe.d``
+(sensible, since 1 is system wide, 2 is kernel or boot specific), and
+modprobe args to override both.
+
+In the ``foo.dyndbg="QUERY"`` form, the query must exclude ``module foo``.
+``foo`` is extracted from the param-name, and applied to each query in
+``QUERY``, and only 1 match-spec of each type is allowed.
+
+The ``dyndbg`` option is a "fake" module parameter, which means:
+
+- modules do not need to define it explicitly
+- every module gets it tacitly, whether they use pr_debug or not
+- it doesn't appear in ``/sys/module/$module/parameters/``
+  To see it, grep the control file, or inspect ``/proc/cmdline.``
+
+For ``CONFIG_DYNAMIC_DEBUG`` kernels, any settings given at boot-time (or
+enabled by ``-DDEBUG`` flag during compilation) can be disabled later via
+the debugfs interface if the debug messages are no longer needed::
+
+   echo "module module_name -p" > /proc/dynamic_debug/control
+
+Examples
+========
+
+::
+
+  // enable the message at line 1603 of file svcsock.c
+  :#> ddcmd 'file svcsock.c line 1603 +p'
+
+  // enable all the messages in file svcsock.c
+  :#> ddcmd 'file svcsock.c +p'
+
+  // enable all the messages in the NFS server module
+  :#> ddcmd 'module nfsd +p'
+
+  // enable all 12 messages in the function svc_process()
+  :#> ddcmd 'func svc_process +p'
+
+  // disable all 12 messages in the function svc_process()
+  :#> ddcmd 'func svc_process -p'
+
+  // enable messages for NFS calls READ, READLINK, READDIR and READDIR+.
+  :#> ddcmd 'format "nfsd: READ" +p'
+
+  // enable messages in files of which the paths include string "usb"
+  :#> ddcmd 'file *usb* +p' > /proc/dynamic_debug/control
+
+  // enable all messages
+  :#> ddcmd '+p' > /proc/dynamic_debug/control
+
+  // add module, function to all enabled messages
+  :#> ddcmd '+mf' > /proc/dynamic_debug/control
+
+  // boot-args example, with newlines and comments for readability
+  Kernel command line: ...
+    // see what's going on in dyndbg=value processing
+    dynamic_debug.verbose=3
+    // enable pr_debugs in the btrfs module (can be builtin or loadable)
+    btrfs.dyndbg="+p"
+    // enable pr_debugs in all files under init/
+    // and the function parse_one, #cmt is stripped
+    dyndbg="file init/* +p #cmt ; func parse_one +p"
+    // enable pr_debugs in 2 functions in a module loaded later
+    pc87360.dyndbg="func pc87360_init_device +p; func pc87360_find +p"
+
+Kernel Configuration
+====================
+
+Dynamic Debug is enabled via kernel config items::
+
+  CONFIG_DYNAMIC_DEBUG=y	# build catalog, enables CORE
+  CONFIG_DYNAMIC_DEBUG_CORE=y	# enable mechanics only, skip catalog
+
+If you do not want to enable dynamic debug globally (i.e. in some embedded
+system), you may set ``CONFIG_DYNAMIC_DEBUG_CORE`` as basic support of dynamic
+debug and add ``ccflags := -DDYNAMIC_DEBUG_MODULE`` into the Makefile of any
+modules which you'd like to dynamically debug later.
+
+
+Kernel *prdbg* API
+==================
+
+The following functions are cataloged and controllable when dynamic
+debug is enabled::
+
+  pr_debug()
+  dev_dbg()
+  print_hex_dump_debug()
+  print_hex_dump_bytes()
+
+Otherwise, they are off by default; ``ccflags += -DDEBUG`` or
+``#define DEBUG`` in a source file will enable them appropriately.
+
+If ``CONFIG_DYNAMIC_DEBUG`` is not set, ``print_hex_dump_debug()`` is
+just a shortcut for ``print_hex_dump(KERN_DEBUG)``.
+
+For ``print_hex_dump_debug()``/``print_hex_dump_bytes()``, format string is
+its ``prefix_str`` argument, if it is constant string; or ``hexdump``
+in case ``prefix_str`` is built dynamically.